This invention relates to a detection and alarm system designed to sense a condition and responsive to that condition to seize a telephone line and notify a central switchboard area of the sensed condition.
An innovative system of this kind is clearly a pressing need especially in the hotel-motel industry as exemplified by recent fatal fires in Las Vegas, Nevada and elsewhere.
Prior systems of this general type have various shortcomings as exemplified by the following U.S. Patents:
1. McCarron, U.S. Pat. No. 2,550,076, upon sensing a condition such as a fire through sensor 50, initiates a dialing mechanism 10 connected in parallel with the phone lines 60, 70 which rings the central switchboard. The deficiencies in this system include the lack of means to seize a line in use, lack ot an audible alarm, and the requirement that the operator call the room for verification.
2. Stendig et al, 3,801,971 discloses an alarm system which has similar purposes as those in the instant disclosure but is usable only in a hotel with internal phone systems in which the operator dials all calls. Any sensation from the hotel room. whether it be lifting of the phone receiver, actuation of a fire or smoke detector, unplugging of the television or unauthorized entry of the room causes a light to actuate at the operator's station which blinks at various frequencies depending upon the condition sensed.
3. Jurschak, U.S. Pat. No. 3,872,253, discloses a system designed for connection to a telephone to automatically transmit information of the existence of an event to a distant location. The main disadvantage of this system is that it is designed only for use in one mode of telephone system state such as when the phone is "on the hook".
4. Dibner, U.S. Pat. No. 3,989,900, shows a system which signals an operator when, for example, the phone in a room has not been used in 24 hours. While the disclosure suggests other triggers such as "burglar or fire sensors" there is no specific disclosure of these details. A further problem is the ability to disarm the system at the phone with switch 13, a feature which could be fatal to a forgetful occupant.
The following patents are also known to applicants but are considered irrelevant to the teachings of the instant invention:
U.S. Pat. No. 1,109,616 to Clement PA1 U.S. Pat. No. 2,525,697 to Lurie PA1 U.S. Pat. No. 4,249,036 to Kutzki